This journal is © The Royal Society of Chemistry … journal is © The Royal Society of Chemistry [year] Supporting information Clean synthesis of p-nitrotoluene from crystalline

Electronic Supplementary Material (ESI) for Green Chemistry This journal is © The Royal Society of Chemistry [year]

Supporting information

Clean synthesis of p-nitrotoluene from crystalline p-nitrobenzylbromide with zero organic discharge

Milan Dinda,a Manoj K. Agrawal,a,b Mahesh R. Gandhi,a Sumesh C. Upadhyay,a Subbarayappa Adimurthy,a Supratim Chakraborty,a and Pushpito K. Ghosh*,a

aCentral Salt and Marine Chemicals Research Institute, Council of Scientific & Industrial Research, G. B. Marg, Bhavnagar –364 002, India

b Present Address: Generic Division, Lupin Research Park, Survey No. 46/47A Nande Village, Mulshi Taluka, Pune 411042, Maharashtra, India

*E-mail: [email protected]; Fax: +91-278-2567562

Warning: p-Nitrobenzyl bromide is a skin irritant and due care must be taken during handling and work up.

Analytical Data

GC-MS Data

Fig S1. GC-MS of 3.0551 g (22.3 mmol) PNT and 2.4084 g (11.15 mmol) PNBBr (2:1, [PNT]:[PNBBr])

in 20 mL EDC for quantification of yields taking into account response factor

Electronic Supplementary Material (ESI) for RSC AdvancesThis journal is © The Royal Society of Chemistry 2012


Fig S2. GC-MS of reaction mixture upon reaction with NBS (5 mmol substrate; 3:1 molar ratio of substrate to reagent) at 80oC under illumination with 100 W tungsten lamp

Fig. S3. GC-MS of reaction mixture upon reaction with BR-S (5 mmol substrate; 3:1 molar ratio of substrate to reagent) at 80oC in the absence of light



Fig. S4. The figure shows the GC-MS of the reaction mixture of Batch 1, Table 1. When corrected for response factor using the data of Figure S1, the observed peak areas of PNT and PNBBr tallied well with the values computed for a 1.9:1.1 molar ratio of PNT to PNBBr expected for quantitative formation of product in Batch 1.

Fig. S5.1. GC-MS of crystallized product from Batch 1
















NaBH4 reduction of the mother liquor after 8th batch:

GC-MS Data:

Figure S6.1 (Table S3, Entry 1)











Fig. S7.1. Mother liquor of Table 1 before debromination with NaBH4

Fig. S7.2. Mother liquor of Table 1 after debromination with NaBH4



Fig. S8. GC-MS of composite of the isolated products from Batches 1- 8, Table 1.



NMR (1H ; 13C NMR) and IR data of PNBBr

1) p - nitrobenzyl bromide (PNBBr) (Table 1, Entry 1, Fig. S5.1)

1H NMR (CDCl3-500 MHz): δ 8.21-8.23 (2H, d, J=8.5); 7.58-7.6 (2H, d, J=8.5); 4.55 (2H, S).

13C NMR (CDCl3-500 MHz): δ 147.7, 144.8, 129.9 (2C), 124.0 (2C), 31.0

13C NMR in CdCl3

1 H NMR in CdCl3



IR data Ѵmax (KBr): 3051, 2840, 2378, 1604, 1534, 1344, 1224, 1099, 1011, 874, 798, 692, 592 cm-1

NMR (1H ; 13C NMR) data of PNBBr2

2) 1-(dibromomethyl)-4-nitrobenzene

1H NMR (CDCl3-200 MHz): δ 8.24-8.2 (2H, d, J=8.6); 7.76-7.72 (2H, d, J=8.4); 6.664 (1H, S).

13C NMR (CDCl3-200 MHz): δ 148.3, 147.9, 127.9 (2C), 124.1 (2C), 38.6 Note: Minor peaks are ascribed to PNT and PNBBr impurities

1H NMR in CdCl3



13C NMR in CdCl3



Table S1. Crystallization studies of 2:1 PNT/PNBBr in CCl4

Entry PNT

g/mmol

PNBBr

g/mmol

CCl4/mL Solid

isolated/g

PNBBr purity

(GC-Area %)

1. 1.0/7.23 0.788/3.64 1.8 1.78 33%

2. 1.0/7.23 0.788/3.64 2.7 1.78 ”

3. 1.0/7.23 0.788/3.64 3.6 1.78 ”

4. 1.0/7.23 0.788/3.64 4.5 0.97 ”

5. 1.0/7.23 0.788/3.64 5.4 0.86 ”

6. 1.0/7.23 0.788/3.64 6.3 0.82 ”

7. 1.0/7.23 0.788/3.64 7.2 0.87 47.6

8. 1.0/7.23 0.788/3.64 8.1 0.73 53.8

9. 1.0/7.23 0.788/3.64 9.0 0.52 65.6

10. 20/145.9 15.76/72.9 162 15.6 64.6



Table S2: Bromination reaction-cum-cold crystallization of PNBBr in CCl4 with recycle of mother liquor

Batch No.

PNT

Kg/ (mol)

Carbon tetrachloride (L)

Br/mole 98% H2SO4 Kg (mol)

PNBBr Kg/(mol)

Purity

(GC area %)

1 0.900 (6.56)

4.8 2.189 0.114 (1.14) 0.364 (1.68)

97.1

2 0.231(1.68) Recycled mother liquor. 1.87

0.107 (1.07) 0.368 (1.7)

95.7

3 0.233 (1.70) Recycled mother liquor. 1.89

0.107 (1.07) 0.369 (1.7)

99.5


0.107 (1.07) 0.373 (1.72)

100


0.095 (0.95) 0.371 (1.71)

98.5


0.107 (1.07) 0.411 (1.9)

96.3


0.107 (1.07) 0.360 (1.66)

100


0.107 (1.07) 0.330 (1.52)

98.8

Total/Av 2.559 (18.63)

4.5L Carbon tetrachloride recovered 15.63

0.851 (8.51)

2.947 (13.59)

98.2

Syntheses details pertaining to Table S2

0.9 kg (6.56 mol) of PNT was dissolved in 4.8 L of CCl4 and added into a 10 L capacity glass

reactor fitted with addition funnel and reflux condenser/distillation assembly. 1.09 L of

brominating agent containing 2.189 mole active Br was added. The contents were heated to



reflux temperature and illuminated externally with 3 x 100 W tungsten filament bulbs. 112 g of

98% H2SO4 (1.14 mol) in 0.6 L of water was taken in the addition funnel and the acid was added

over a period of 2 h. (Caution: If the reaction mass develops brown color stop the addition and

allow color to disappear before continuing addition of acid.) Reflux conditions were maintained

for an additional 1 h. The reaction mass was allowed to cool to ca. 40oC temperature and the

contents discharged into a separating column. The organic phase was poured into a suitable wide

mouth glass vessel and kept for crystallization in a deep freezer after inserting 3 broomsticks to

promote crystallization. The organic phase attained a temperature of -15oC and was removed

after 12 hours. Crystal formation was seen. The contents were allowed to warm up to 0-4oC to

re-dissolve PNT which had co-crystallized with the product. The lumps of crystals were broken

up and the contents centrifuged in a continuous centrifuge, which operation required barely a

couple of minutes. The collected PNBBr weighed 0.364 kg (1.68 mol) and exhibited 97.1% (GC

area %) purity. The mother liquor was placed back into the glass reactor. Fresh 0.231 kg (1.68

mol) of PNT, equivalent to the amount of PNBBr recovered in the first batch, was added and

brominating reagent was taken at the mole ratio as shown in Table S2 below. The reaction was

repeated in the same manner as above but towards the end of the reaction 0.6 L of CCl4 was

collected by changing over from reflux mode to distillation mode and kept for chilling. Cold

crystallization was repeated to obtain PNBBr from the reaction mass. The crude PNBBr was

washed in the centrifuge with the chilled CCl4 and centrifuged. The mother liquor and washings

were once again recycled. Eight batches were carried out in all and the data on PNBBr yield and

purity for each batch and also the total yield and average purity are provided in the table S2.

After the 8th batch, CCl4 was recovered from the mother liquor and the residue was then

subjected to vacuum distillation. For this purpose, the residue was first melted and purged with



nitrogen. Thereafter the temperature was raised to 140-155oC and the PNT distilled over at the

reduced pressure of 10-40 mm Hg. The amount of PNT recovered was 0.514 kg (3.75 mol).

Table S3.Optimization of NaBH4 concentration for the reduction of mother liquor obtained in Batch 8,

Table 1 of manuscript

Entry

No.

NaBH4 taken (with respect to the amount of

PNBBr2 (1) present in the reaction mixture)

% PNBBr2 (1) % PNBBr % PNT

1. 0 equiv. 80.72 19.23 0.0

2. 2 equiv. 58.46 41.56 0.0

3. 4 equiv. 52.14 47.86 0.0

4. 6 equiv. 22.63 77.37 0.0

5. 8 equiv. 4.94 69.35 25.7

A solution was prepared by mixing PNBBr2 and PNBBr for the optimization reaction of NaBH4 reduction (from the GC-MS the initial mixture was found to be consisted of 80.72% PNBBr2 and 19.23% PNT). Reduction reactions were carried out at room temperature with constant stirring for 2.5 h and solvent system was EDC and a few drops of methanol. Work-up was done using EDC-water mixture and with a small portion of separated organic layer GC-MS were recorded.



Mass Balance related to the experimental results of Tables 1 and 2 in the manuscript

Table S4. Computation of Isolated yield of PNBBr with respect to PNT consumed and reagent utilized based on the data of Tables 1 and 2 and response factors computed from Figure S1.

1. Total PNT taken 746.0 mmol

2. PNT remaining in treated mother liquor suitable for perennial recycle

58.61 mmol

3. PNT which could have been separated from product through more efficient washing and recycled along with treated mother liquor of Batch 8, Table 1

28.54 mmol

4. Net PNT consumed 658.95 mmol

5. Total Br equivalents in BR-S taken 659.2

5. Gross weight of crystalline PNBBr obtained (96.9 % purity w/w)

126.3 g

6. Actual PNBBr amount in solid product in g/mmol 122.39 g

566.62 mmol

7. PNBBr in treated mother liquor suitable for perennial recycle

81.15 mmol

8. Total isolated and recoverable PNBBr 647.77 mmol

9. Yield of isolated and recoverable PNBBr with respect to PNT amount actually consumed and considering recycle of the rest of the amount taken

98.30

10. Yield of isolated and recoverable PNBBr with respect to “Br” equivalents in BR-S amount taken

98.26


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This journal is © The Royal Society of Chemistry … journal is © The Royal Society of Chemistry [year] Supporting information Clean synthesis of p-nitrotoluene from crystalline